Traffic signal control system

ABSTRACT

A system for controlling the traffic signal lights at an intersection where at least two streets cross, which comprises: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; means for receiving said detection signal to produce an actuation signal when said detection signal continues for a predetermined period of time; and control means operable in response to said actuation signal to control said signal lights. The system may further include means for causing said actuation signal producing means to be operative only when right-of-way is not given to said one street. With no right-of-way being given to said one street, when a vehicle arriving at the intersection from said one street to be stopped and stay in said detection zone for said predetermined period of time, said actuation signal is produced to actuate said control means to control said signal lights so as to give rightof-way to said one street. The system may still further include means for applying said detection signal as an alternative actuation signal to said control means when right-of-way is given to said one street, so that said control means operates to extend the period of said right-of-way for said one street, thereby allowing the vehicle that has caused said detection signal to pass through said intersection.

TRAFFIC SIGNAL CONTROL SYSTEM [72] Inventors: Sadayuki Uryu, Osaka; I-lirosi Ueda,

Kyoto, both of Japan [7 3] Assignee: Omron Tateisi Electronics Co,

Kyoto, Japan [22] Filed: Feb. 6, 1970 [21] Appl. No.: 9,140

30 Foreign Application Priority Data Feb. 15, 1969 Japan ......44/11365 52 us. Cl. ..340/37, 340/31 R [51] Int. Cl. ..G08g 1/07 [58] Field of Search ..340/31 R, 36, 38 S, 39, 37,

[56] References Cited v UNITED STATES PATENTS 2,130,013 9/ 1938 Hunter ..340/36 2,090,619 8/1937 Biach et al ..340/36 3,150,349 9/1964 Wilcox ..340/ 37 3,234,505 2/ 1966 Du Vivier ..340/37 3,529,285 9/1970 Wapner ..340/37 Primary Examiner-Kathleen H. Claffy Assistant Examiner-Randall P. Myers Att0rney-Christensen, Sanborn & Matthews 7] ABSCT A system for controlling the traffic signal lights at an intersection where at least two streets cross, which comprises: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; means for receiving said detection signal to produce an actuation signal when said detection signal continues for a predetermined period of time; and control means operable in response to said actuation signal to control said signal lights. The system may further include means for causing said actuation signal producing means to be operative only when right-of-way is not given to said one street. With no right-of-way being given to said one street, when a vehicle arriving at the intersection from said one street to be stopped and stay in said detection zone for said predetermined period of time, said actuation signal is produced to actuate said control means to control said signal lights so as to give right-of-way to said one street. The system may still further include means for applying said detection signal as an alternative actuation signal to said control means when right-of-way is given to said one street, so that said control means operates to extend the period of said right-of-way for said one street, thereby allowing the vehicle that has caused said detection signal to pass through said intersection.

2Claims,2DrawingFigures 3m /2R 9' 10 VEHICLE .8 l 8mm 10 DETECTOR M AND TIMER g SIGNAL HR VEHICLE Ann YE SIGNAL 0 DETECTOR d D 8 0 3b) a s im.

Patented .Aug. 29, 1912 3,688,254

A v 3b 1 I 2R 3G\ Q VEHICLE 4 L l 8 i DETECTOR AND TIMER r- OR 1 SIGNAL VEHlCLE )C m slam 50 02mm d D u 0 3b) SIGNAL AT T EDRNEYS TRAFFIC SIGNAL CONTROL SYSTEM This invention relates to a traffic signal control system and more particularly to a traffic signal control system of a semi-traffic-actuated type.

As is well known, this type of system is such that preference or right-of-way is normally given to the-traftie on the major street until a vehicle arrives on the minor street crossing the major street, whereupon the right-of-way is transferred from the major to minor streets. To detect the arrival of a vehicle on the minor street, a vehicle detector is usually provided on the minor street immediately in front of the street intersection. With such a vehicle detector placed nearthe intersection and in case the minor street is of a relatively small width, if a vehicle on the major street turns right or left into the minor street, it may well happen that the vehicle trespasses the detection zone of the vehicle detector on the minor street and actuates the detector to produce a detection signal. Then, despite the fact there is no proper demand from the minor street for the right-of-way to be transferred to the minor street, the existence of such a demand is erroneously recognized so as to turn the red signal to green for the minor street. This will certainly reduce the efficiency of the traffic signal control at the street intersection.

Accordingly, it is one object of the invention to provide a traffic signal control system which is capable of properly recognizing any demand for a right-of-way by traffic on the minor street for proper control of the traffie signals at a street intersection.

Another object of the invention is to provide a traffic signal control system which is capable of correctly determining whether or not the detection signal produced by a vehicle detector on the minor street has been caused by a vehicle thereon truly deserving the demand for right-of-way.

Another object of the invention is to provide a traffic signal control system wherein if the detection signal produced by a vehicle detector on the minor street when right-of-way is not given to the minor street does not continue for a predetermined period of time, the detection signal is recognized as the one not expressing any demand for right-of-way for the minor street, whereas when the detection signal continues longer than the predetermined period of time, it is recognized as the signal expressing a proper demand for the rightof-way to be transfered to the minor street, whereby any demand on the minor street for right-of-way can be correctly detected.

Still another object of the invention is to provide a traffic signal control system wherein if the detection signal produced by a vehicle detector on the minor street continues longer than a predetermined period of time when right-of-way is not given to the minor street, or if a detection signal is produced while right-of-way is being given to the minor street, the signal is recognized as expressing a proper demand for right-of-way on the minor street, whereas if the detection signal does not continue for a predetermined period of time when right-of-way is not given to the minor street, the detection signal is recognized as not expressing any proper demand for right-of-way on the minor street, whereby the traffic signal control at the intersection can be performed only on the basis of the detection signal expressing the proper demand for right-of-way on the minor street.

In accordance with the invention, if the detection signal produced by a vehicle detector provided on the minor street continues for a predetermined period of time when right-of-way is not given to the minor street, or if a detection signal is produced when right-of-way is given to the minor street, the detection signal is recognized as having been caused by a vehicle on the minor street demanding for transfer of the right-of-way to the minor street or for extension of the right-of-way period therefor, so that the traffic signals at the intersection are controlled accordingly on the basis of the detection signal. Therefor, even when a vehicle coming along the major street turns right or left at the intersection into the minor street so as to pass through the detection zone of the vehicle detector provided thereon, the vehicle never stays within the detection zone very long, so that the detection signal produced by the detector will not continue long enough to affect the signal control at the street intersection. However, if a vehicle is stopped on the minor street in front of the intersection, it will stay in the detection zone of the detector so that the detection signal continues for the predetermined period of time. Therefore, the detection signal is recognized as expressing a proper demand for transfer of the right-ofway to the minor street.

The detection signal produced when right-of-way is given to the minor street expresses a proper demand for extension of the right-of-way period by a vehicle on the minor street, since at this time there cannot be any vehicle on themajor street turning right or left into the minor street. Therefore, this detection signal may be used to control the traffic signals in such a manner that the green time for the minor street is extended.

The invention will become more apparent from the following detailed description of a preferred embodiment thereof with reference to the accompanying drawings, wherein;

FIG. 1 is a schematic top plan view of a street intersection to which the system of the invention may be applied; and

FIG. 2 is an electrical block diagram showing a general layout of the system of the invention.

Referring in detail to FIG. 1, there is shown a street intersection 12 where a major street 1 and a minor street 2 cross, with a pair of signal lights 10 for traffic in opposite directions on the major street and another pair of signal lights 20 for traffic in opposite directions on the minor street. A controller 9 (FIG. 2) controls the illumination of the signal lights in a known sequential manner. The type of control here employed is a semi-traffic-actuated type.

A pair of vehicle detectors 3a and 3b are provided on the minor street at opposite sides of the intersection so as to detect vehicles approaching thereto. The detectors may be of any suitable type, but in the illustrated embodiment they are supersonic presence detectors. As is well known, this type of detector is such that it is mounted on top of a pole planted alongside the street and projects supersonic waves downwardly onto a predetermined detection zone A on the street. The presence of a vehicle in the zone can be detected by the supersonic waves reflected by the vehicle which are different from the waves reflected by the surface of the street.

When the signals 10 turn to green, trafiic on the major street starts moving, some vehicle going straight toward the north 1! and others turning right 11a or left 1112 into the minor street. The same is true with southbound traffic at the opposite side of the intersection. With right-of-way being given to the major street, any vehicle coming along the minor street is stopped in front of the intersection due to the red signal being displayed thereto at this time. The detector 3a or 317 then detects the vehicle that has been stopped within the detection zone A and produces a detection signal. Upon recognition of this detection signal as expressing the presence of a vehicle on the minor street duly demanding for the right-of-way to be transferred thereto, the controller 9 controls the signal lights 10 and 20 accordingly, as will be described later in detail.

Under the same condition, that is, with right-of-way given to the major street, if a vehicle from the major street turns right or left into the minor street to pass the detection zone A, the detector 3a or 3b produces a detection signal. If the controller 9 should operate in response to that detection signal, it would change-the signal lights to transfer the right-of-way to the minor street despite the absence of any demand for such transfer on the minor street. On the other hand, if under the same condition, that is, with right-of-way given to the major street, a vehicle on the minor street approaching the intersection in the direction of an arrow 21 enters the detection zone A, the detector 3a or 3b produces a detection signal. In this case, the detection signal duly expresses the presence of a proper demand for the right-of-way to be transferred to the minor street. Therefore, for proper control of the traffic signals, it is necessary to distinguish between the above two kinds of detection signals, that is, to determine whether or not the present detection signal has been caused by the presence of a vehicle truly deserving right-of-way.

Directed toward this end is the arrangement of FIG. 2, wherein the detection signal produced by the detector 3a or 3b is applied to an OR element 4. The output d from the OR element is applied as one input to AND elements 5 and 6. The controller 9 is so arranged that it produces a signal on a line 2R when the minor street signal lights 20 remain red, and a signal on a line 2G while the same signal lights 20 are green. The signals on the lines 2R and 26 will be referred to as 2R and 26, respectively hereinafter. The signals 2R and 2G are applied as the other input to the AND elements 5 and 6, respectively.

The output from the AND element 5 is applied through timer 7 to and OR element 8, to which the output from the AND element 6 is directly applied. The timer 7 is of the on-delay type that produces an output only when the input thereto lasts for a predetermined period of time. This period of time is set to a length longer than the time required for a vehicle on the major street turning right or left into the minor street to pass completely through the detection zone A.

The output D from the OR element 8 is applied as to the controller 9, which controls the signal lights 10 and 20 by turning on and off thereof or extending the rightof-way period for the minor street.

Under the condition that the minor street 2 is given no right-of-way, that is, the signal lights 20 to the minor receives two inputs so as to produce an output to be applied to the timer 7. If the detection signal has been caused by a right or left turning vehicle from the major street, the output d disappears before lapse of the time set by the timer 7, so that no output is produced by the timer. As a result, no change is caused to occur in the controlling operation of the controller 9 and the signal lights 10 to the major street are kept green. However, if

the detection signal has been caused by a vehicle coming along the minor street and having been stopped in the detection zone A, the signal and consequently the output signal d from the OR element 4 continues longer than the time set by the timer 7, so that the timer produces an actuation signal to be applied to the OR element 8. The output D from the OR element 8 actuates the controller 9, so that upon lapse of the minimum green time for the major street, the signal lights 20 are turned green.

Thus, when the right-of-way has been transferred to the minor street, the controller 9 produces a signal 2G to be applied to the AND element 6. At this time, the

signal 2R does not exist any longer, so that the AND element 6 alone and not the AND element 5 receives one input. Under the condition, when the signal d is produced, the AND element 6 produces an output to be applied directly to the OR element 8 as an alternative actuation signal. At this time, the output D from the OR element 8 causes the controller 9 to extend the green time of the signal lights 20 for the minor street 2 by one unit length of extension.

So long as the minor street has right-of-way, there cannot by any right or left turn vehicle coming from the major street, so that there is no problem in applying all detection signals to the controller 9. When the signal D is not caused to appear by a succeeding vehicle on the minor street during the unit extension, the right-ofway is returned to the major street.

What we claim is:

1. A system for controlling the traffic signal lights at an intersection where at least two streets cross, comprising: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; a controller for controlling sequential illu mination of said signal lights, said controller providing a first signal when right-of-way is given to the other of said streets and a second signal when said right-of-way has been transferred to said one street; a first AND element receiving as one input said detection signal and as the other input said first signal from said controller to produce an output; a timer receiving said first AND element output to produce an actuation signal when said first AND element output has lasted for a predetermined period of time, said actuation signal being applied to said controller to control said signal lights for transfer of said right-of-way from said other street to said one street; and a second AND element receiving as one input said detection signal and as the other input said second signal from said controller to produce an output to be applied as an alternative actuation signal to said controller for extension of the right-of-way period for said one street.

2. A system for controlling the trafiic signal lights at an intersection where at least .two streets cross, comprising: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; means receiving said detection signal to produce an actuation signal when said detection signal continues for a predetermined period of time, saidreceiving means including means enabling production of said actuation signal only when right-of-way is not given to said one street; control means operable in response to said actuation signal to control said signal lights; and wherein said receiving means further in- 

1. A system for controlling the traffic signal lights at an intersection where at least two streets cross, comprising: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; a controller for controlling sequential illumination of said signal lights, said controller providing a first signal when right-of-way is given to the other of said streets and a second signal when said right-of-way has been transferred to said one street; a first AND element receiving as one input said detection signal and as the other input said first signal from said controller to produce an output; a timer receiving said first AND element output to produce an actuation signal when said first AND element output has lasted for a predetermined period of time, said actuation signal being applied to said controller to control said signal lights for transfer of said right-of-way from said other street to said one street; and a second AND element receiving as one input said detection signal and as the other input said second signal from said controller to produce an output to be applied as an alternative actuation signal to said controller for extension of the right-of-way period for said one street.
 2. A system for controlling the traffic signal lights at an intersection where at least two streets cross, comprising: a vehicle detector having a predetermined detection zone and provided on one of said streets at each side of said intersection to produce a detection signal in response to the presence of a vehicle within said detection zone; means receiving said detection signal to produce an actuation signal when said detection signal continues for a predetermined period of time, said receiving means including means enabling production of said actuation signal only when right-of-way is not given to said one street; control means operable in response to said actuation signal to control said signal lights; and wherein said receiving means further includes means for applying said detection signal as an alternative actuation signal to said control means when right-of-way is given to said one street, so that said control means operates to extend said right-of-way. 